Packet transmission scheduling technique

ABSTRACT

A packet data transmission method of the HSDPA system includes collecting information on the quality of physical channels, a status of the MAC buffer, the priority level of data, the delay of data, and the like, determining the transmission order of data and the size of a data block to be transmitted based on the collected information, and transmitting the data block through the physical layer according to the order of transmissions. Since the HSDPA scheduler takes into account the delay of data, the quality of real-time services can be improved.

This application is a continuation of and claims benefit of U.S. patentapplication Ser. No. 12/178,741, filed Jul. 24, 2008 now U.S. Pat. No.7,619,985, which is a continuation of U.S. patent application Ser. No.10/301,625, filed Nov. 22, 2002 now U.S. Pat. No. 7,515 616, and claimspriority to Korean Patent Application Serial No. KR 73641/2001, filed inthe Republic of Korea on Nov. 24, 2001 and Korean Patent ApplicationSerial No. KR 00631/2002, filed in the Republic of Korea on Jan. 5,2002, the contents of each of the above-recited applications areincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly to packet transmission scheduling of the High SpeedDownlink Packet Access (HSDPA) system operated in a UMTS terrestrialradio access network (UTRAN).

2. Background of the Related Art

The Universal Mobile Telecommunications System (UMTS) is a thirdgeneration mobile communication system, which evolved from a GlobalSystem for Mobile Communications (GSM) and a European style mobilecommunication standard. It is intended to provide improved mobilecommunication services based on a GSM core network (CN) and WidebandCode Division Multiple Access (WCDMA) access technology.

For the purpose of making a standard for third generation mobilecommunication systems (IMT-2000 systems) based on GSM core network andWCDMA radio access technology, a group of standard developingorganizations, including ETSI of Europe, ARIB/TTC of Japan, T1 of U.S.,and TTA of Korea, established the Third Generation Partnership Project(3GPP).

For the purpose of efficient management and technological development,five Technical Specification Groups (TSGs) were organized under the 3GPPin consideration of network construction factors and their operations.

Each TSG is responsible for approving, developing, and managingspecifications related to a pertinent area. Among them, the Radio AccessNetwork (RAN) group has developed functions, requirements, and interfacespecifications related to UE and UMTS terrestrial radio access network(UTRAN) in order to establish a new radio access network specificationto the third generation mobile communication system.

The TSG-RAN group consists of one plenary group and four working groups.Working Group 1 (WG1) has been developing specifications for a physicallayer (Layer 1) and WG2 has been specifying functions of a data linklayer (Layer 2) between UE and UTRAN. In addition, WG3 has beendeveloping specifications for interfaces among Node Bs (the Node B is akind of base station in the wireless communications), Radio NetworkControllers (RNCs), and the core network. Lastly, WG4 has beendiscussing requirements for radio link performance and radio resourcemanagement.

FIG. 1 illustrates a structure of the UTRAN defined in 3GPP. As shown inFIG. 1, the UTRAN 110 includes at least one radio network sub-systems(RNSs) 120 and 130. Each RNS 120, 130 includes an RNC 121, 131 and atleast one or more Node Bs 122, 123, 132, 133. For example, Node B 122 ismanaged by RNC 121, and receives information transmitted from thephysical layer of the UE 150 through an uplink channel and transmits adata to the UE 150 through a downlink channel.

Accordingly, the Node B acts as an access point of the UTRAN from the UEpoint of view.

The RNCs 121 and 131 allocate and manage radio resources of the UMTS andare connected to a suitable element of the core network 140 depending ontypes of services provided to users.

For example, the RNCs 121 and 131 are connected to a mobile switchingcenter (MSC) 141 for a circuit-switched communication such as a voicecall service, and are connected to a Serving GPRS Support Node (SGSN)142 for packet switched communication such as a wireless Internetservice.

The RNC in charge of a direct management of the Node B is called aControl RNC (CRNC). The CRNC manages common radio resources.

On the other hand, the RNC that manages dedicated radio resources for aspecific UE is called a Serving RNC (SRNC). The CRNC and the SRNC can beco-located in the same physical node. However, if the UE has been movedto an area of a new RNC that is different from SRNC, the CRNC and theSRNC may be located at physically different places.

There is an interface that can operate as a communication path betweenvarious network elements. The interface between a Node B and a RNC iscalled a lub interface, and an interface between RNCs is called a lurinterface. And an interface between the RNC and the core network iscalled a lu interface.

FIG. 2 illustrates a protocol structure of a radio interface protocoldefined in the 3GPP. As shown in FIG. 2, the radio interface protocolhorizontally includes a physical layer, a data link layer, and a networklayer, and is vertically divided into a control plane for transmissionof control information (signaling) and a user plane for transmission ofdata information.

The user plane is a region through which user traffic such as voiceinformation or IP (Internet Protocol) packets is transmitted, and thecontrol plane is a region through which control information required fornetwork maintenance and management is transmitted.

Of the layers, the physical layer (PHY) handles transmission of datausing a wireless physical channel between the UE and the UTRAN. Thetypical functions of the physical layer include data multiplexing,channel coding, spreading, and modulation.

The physical layer exchanges information with a Medium Access Control(MAC) layer through a transport channel. The transport channel isclassified into a dedicated transport channel and a common transportchannel depending on whether its use is dedicated to one UE or whetherit is shared among several UEs.

The MAC layer transmits data by using a suitable mapping between logicalchannels and transport channels. The MAC layer is internally dividedinto two sub-layers, to with a MAC-d sub-layer which manages thededicated transport channel, and a MAC-c/sh sub-layer which manages thecommon transport channel. The MAC-d sub-layer is located in the SRNC andthe MAC-c/sh sub-layer is located in the CRNC.

There are various kinds of logical channels according to what kind ofinformation the channel carries. The logical channel can be divided intotwo channels. One logical channel is a control channel for transmissionof the control plane information and the other is a traffic channel fortransmission of the user plane information.

The radio link control (RLC) layer is responsible for reliabletransmission of RLC protocol data units (PDUs). The RLC may segment orconcatenate RLC service data units (SDUs) delivered from the higherlayer. If the RLC PDUs are ready, they are delivered to the MAC layerand transmitted sequentially to the other node (UE or UTRAN). Sometimes,the RLC PDU can be lost during the transmission. In this case, the lostPDU can be retransmitted. The retransmission function of the RLC layeris called an Automatic Repeat reQuest (ARQ).

The RLC layer may include several RLC entities. Each of them performs anindependent radio link control function. The operation mode of each RLCentity is one of transparent mode (TM), an unacknowledged mode (UM), andan acknowledged mode (AM) depending on the adopted functions.

The Packet Data Convergence Protocol (PDCP) layer is positioned over theRLC layer and efficiently transmits data of network protocols such asIPv4 or IPv6. For example, a header compression method in which headerinformation of a packet is reduced can be used. The PDCP layer mayinclude several independent PDCP entities like the RLC layer. TheBroadcast/Multicast Control (BMC) layer is responsible for transmittingbroadcast messages from a Cell Broadcast Center (CBS) positioned at acore network. The primary function of BMC is to schedule and transmitcell broadcast messages destined for a UE. The BMC layer, in general,uses an RLC entity operated in the unacknowledged mode in order totransmit broadcast messages.

Finally, the Radio Resource Control (RRC) layer is a layer defined inthe control plane. The RRC performs functions of establishment,reestablishment, and release of radio resources. In addition, the RRClayer can exchange control information between UE and UTRAN using RRCmessages.

The maximum transmission rate of UMTS is 2 Mbps in the indoor andpico-cell environment, and 384 Kbps in the outdoor environment. However,as wireless Internet services have become popular, various servicesrequire higher data rates and higher capacity. Although UMTS has beendesigned to support multimedia wireless services, the maximum data rateof 2 Mbps is not enough to satisfy the required quality of services.Therefore, the 3GPP is conducting research directed to providing anenhanced data rate and radio capacity. One result of the research is theHigh Speed Downlink Packet Access (HSDPA). The purpose of the HSDPAsystem is to provide a maximum data rate of 10 Mbps and to improve theradio capacity in the downlink.

Various techniques in the HSDPA system include Link Adaptation (LA) andHybrid Automatic Repeat reQuest (HARQ).

In the LA method, the UTRAN can choose the appropriate modulation andcoding scheme (MCS) according to the channel condition. For example, ifthe channel condition is good, LA uses 16 Quadrature AmplitudeModulation (QAM) to increase the throughput. If a channel condition isnot as good, however, LA uses Quadrature Phase Shift Keying (QPSK) toincrease the probability of success.

The HARQ method retransmits lost packets, but the exact operation isdifferent than the retransmission method in the RLC layer. If one packetis corrupted during transmission, HARQ transmits another packet thatcontains the additional information for recovery. The retransmittedpacket and the original packet are combined in the receiver. Theretransmitted packet may contain the same information as that of thepreviously transmitted data, or may contain any additional supplementaryinformation for data recovery.

Since the HSDPA system is an evolutional form of the UMTS system, theconventional UMTS network needs to be maintained as much as possible tosupport backward compatibility and to reduce the cost of networkdeployment. However, some minor changes are inevitable.

To reduce the impact of the changes, most of the features are supportedin Node B. This means that other parts of the UMTS network will not beaffected. Accordingly, some functions in Node B need to be changed andsome MAC functions are transferred from RNC. The MAC functionalitiesconstitute a new MAC sublayer in Node B and it is called “MAC-hs”sublayer.

The MAC-hs sublayer is placed above the physical layer, and performspacket scheduling and various other functions (including HARQ and LA).In addition, the MAC-hs sublayer manages a transport channel called anHSDPA—Downlink Shared Channel (HS-DSCH), which is used to deliver datafrom the MAC-hs sublayer to the physical layer.

FIG. 3 shows a structure of a radio interface protocol for the HSDPAsystem. As shown in FIG. 3, the MAC-hs sublayer is placed over thephysical layer (PHY) in the Node B. In both the UE and UTRAN, the MAC-hssublayer transfers data to the upper layer through MAC-c/sh and MAC-dsublayers. The MAC-c/sh and the MAC-d sublayers are located in the CRNCand the SRNC, respectively, as in the related art system. In FIG. 3, anHS-DSCH Frame Protocol (FP) delivers the HSDPA data on the lub or thelur interface.

FIG. 4 illustrates the structure of the MAC layer in the HSDPA system.As shown in FIG. 4, the MAC layer is divided into a MAC-d sublayer 161,a MAC-c/sh sublayer 162, and a MAC-hs sublayer 163. The MAC-d sublayer161 is in the SRNC and manages dedicated logical channels. The MAC-c/shsublayer 162 is located in the CRNC and manages a common transportchannel. The MAC-hs sublayer 163 is located in the Node B and managesthe HS-DSCH.

In the HSDPA system, the MAC-c/sh sublayer 162 controls the data flowbetween the MAC-d sublayer 161 and the MAC-hs sublayer 163. The flowcontrol function is used to prevent data from being discarded duringnetwork congestion, and to reduce the time delay of signaling signals.The flow control can be performed independently according to a priorityof data transmitted through each HS-DSCH.

The HARQ function, as stated previously, improves the efficiency of datatransmission. In the Node B, the MAC-hs sublayer 163 contains one HARQblock that supports the HARQ function. The HARQ block includes severalHARQ entities for controlling a HARQ operation of each UE. There is oneHARQ entity for each UE in the HARQ block.

Moreover, there are several HARQ processes inside each HARQ entity. EachHARQ process is used for transmission of the “data block,” which iscomposed of one or more MAC MAC-hs SDUs. The data block is processed oneby one in the HARQ process.

If the specific data block is successfully transmitted, the HARQ processcan treat another data block. If the transmission fails, the HARQprocess retransmits the data block until the data block is eithersuccessfully transmitted or discarded. The number of MAC-hs SDUsconstituting the data block differs depending on the status of the radiochannel. If the channel is in a good condition, it can transmit moreMAC-hs SDUs. Conversely, if the channel is in a bad condition, it cantransmit fewer MAC-hs SDUs, and therefore a relatively small number ofMAC-hs SDUs comprises a data block.

The scheduling block determines the size of the data block based on theinformation (channel condition) from the physical layer. Each data blockcan be transmitted in the unit of Transmission Time Interval (TTI) whichis 2 ms in the HSDPA system. In addition, the scheduling function of theNode B determines the order of the data transmission according to thepriorities of data. The scheduling block adds a priority classidentifier (PCI) and a transmission sequence number (TSN) to the datablock and delivers it to a suitable HARQ process. If the transmission ofthe data block is not successful, the identical data block isretransmitted.

The TFC selection function selects the appropriate transport format ofeach HS-DSCH when several HS-DSCHs are used for the data transmission.The transmission procedure is described with reference to FIG. 4.

The channel switching block in the MAC-d layer determines thetransmission path of the PLC PDU, which is transferred through aDedicated Traffic Channel (DTCH) or a Dedicated Control Channel (DCCH)from the RLC layer. If the RLC PDU is going to be transmitted to theDedicated channel (DCH), a header field is added into the PDU and it istransmitted to the physical layer through the DCH. If the HS-DSCHchannel is used, the RLC PDU is transmitted to the MAC-c/sh sublayer 162through a transmission channel multiplexer (T/C MUX). The T/C MUX addsidentification information into the header of the PDU in order toidentify the logical channel to which each data belongs.

Upon receiving the RLC PDU, the MAC-c/sh sublayer 162 transfers thepacket to the MAC-hs sublayer 163. Subsequently, the data transmitted tothe MAC-hs sublayer is stored in a buffer of the MAC-hs sublayer 163 andconstructed as a data block with a suitable size. The schedulingfunction determines the size of the data block based on the channelcondition. Next, the PCI and TSN are added to the data block, and it isdelivered to the HARQ process by the scheduling function.

FIG. 5 illustrates an operation of the scheduling block of the MAC-hssublayer in Node B. As shown in FIG. 5, the HSDPA scheduler 174 receivesinformation regarding a data priority and an amount of stored data froma storage unit 171, and receives channel status information from thephysical layer 173 (S101, S102).

The storage unit 171 is preferably a soft memory in which data can beeasily erased and written, and stores the MAC-hs SDUs delivered from anupper layer.

The scheduler 174 controls the operations of the storage unit 171 andthe HARQ entity 172 based on the information (steps S103, S104). Thescheduler 174 determines the size of the data block, and constitutes thedata block, and adds PCI and TSN fields in the data block. Next, thescheduler 174 transmits the corresponding data block to a suitable HARQprocess in the HARQ entity, where the data block will be transmittedthrough the physical layer.

If the data block is successfully transmitted, the corresponding data inthe storage unit 171 is deleted based on the feedback information (stepS105). At the same time, the HARQ block reports to the scheduler 174whether or not the data block has been successfully transmitted. Usingthe transmission result, the scheduler 174 can adjust the transmissionof data blocks (step S106).

In general, overall system efficiency and capacity can be determined byan adopted scheduling algorithm. Therefore, the scheduling algorithmshould be suitable for characteristics of the provided service.

A scheduling algorithm used in the HSDPA system is currently based onthe priority information of each data. The scheduler monitors data inthe storage unit of the MAC-hs sublayer, and transmits the data blockhaving the higher priority.

The priority information of each data (MAC-hs SDU) is transferredthrough a HS-DSCH FP (Frame Protocol) between the Node B and the RNC.

FIG. 6 illustrates a structure of the frame structure of the HS-DSCH FPin the HSDPA system. Referring to FIG. 6, CmCH-PI (Common ChannelPriority Indicator) field indicates a priority of the MAC-hs SDUsincluded in the corresponding data frame, and has values of 0-15. ‘0’signifies the lowest priority, while “15” signifies the highestpriority.

Even though the data priority is the main factor in the HSDPA scheduler,the information is only defined in the specific services. Servicessupported by the HSDPA include streaming services such as video ondemand (VOD) and Audio on demand (AOD), interactive services such as Webbrowsing and file downloading, and background services such as e-mailand background data downloading. Among these services, the data priorityis defined only for interactive services and background services. Thishas been true so far because the related art streaming services areprovided by dedicated resources rather than common resources. However,the HSDPA system provides various services with the common resources.

Additionally, unlike other types of services, the service quality ofstreaming services is not guaranteed simply by the priority informationbecause data of streaming services are real-time and delay-sensitive.That means there is no need to use the priority information of the dataof streaming services.

Typically, real-time data will be lost if the delay of the data exceedsa certain delay limit. In order to reduce the loss of real-time data,the scheduler should take traffic characteristics of streaming servicesinto consideration.

Because the current HSDPA scheduler operates based on the priorities ofpackets, the HSDPA scheduler may be suitable for non-real-time services(i.e. interactive services and background services). For teal-timeservices, however, the delay is the most important factor in scheduling.Consequently, there is a problem with the related art scheduler of HSDPAin that is does not take the delay component into account when thesupporting services include streaming services.

The above references are incorporated by reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

SUMMARY OF THE INVENTION

An object of the invention is to solve at least the above problemsand/or disadvantages and to provide at least the advantages describedhereinafter.

It is another object of the present invention is to provide a packettransmission scheduling method of the HSDPA system suitable for trafficcharacteristics of each service in a multimedia environment wherereal-time and non-real-time data coexist, thereby enhancing a servicequality.

It is another object of the present invention to provide a packettransmission scheduling method of the HSDPA system based on both delayinformation as well as data priorities in the Node B where real-time andnon-real-time data coexist.

It is another object of the present invention to provide a packettransmission scheduling method of the HSDPA system that considers thedelay information in the RLC layer and the delay in the MAC layer forreal-time services.

It is another object of the present invention to deliver delayinformation or priority information of data in the RLC layer to theHSDPA scheduler by using the frame format of the frame protocol, whichcan contain the related control information.

To achieve at least the above objects in whole or in parts, there isprovided a packet data transmission method of the HSDPA system,including the steps of: collecting information on the quality ofphysical channels, the status of the MAC buffer, the priority level ofdata, the delay of data, and the like; determining the transmissionorder of data and the size of a data block to be transmitted based onthe collected information; and transmitting the data block through thephysical layer according to the order of transmissions.

In the data transmission method of the HSDPA system of the preferredembodiment, the delay information of data means the delayed periodduring which the data remains in the MAC layer, or the total delayedperiod during which the data remains in the MAC layer and the upperlayer. Also the delay information in the MAC layer is preferablymeasured by a timer provided in the MAC layer, and the delay informationin the upper layer can be measured by an additional timer or by a timerdesigned for the specific use in the upper layer. Moreover, the delayinformation in the upper layer is preferably transferred together withdata themselves by using a frame protocol on the lub or lur interface.

In a first embodiment of the present invention, the frame protocol usestwo frame formats. The frame protocol preferably selects one of the twoframe formats depending on the type of data to be transmitted. Bothheaders of the two formats include the data type field to identify thetype of data. The first frame format of the frame protocol preferablyincludes the data priority field, and the second frame format preferablyincludes the delay field. If the data to be transmitted isnon-real-time, the frame protocol transmits the data together withpriority information by using the first format. If the data isreal-time, the frame protocol transmits the data together with the delayinformation in the upper layer by using the second format.

In a second embodiment of the present invention, the frame format of theframe protocol preferably includes all of the priority field and thedelay field. Thus, if the data to be transmitted is non-real-time, thepriority field is set, while if the data to be transmitted is real-time,the delay field is set.

In a third embodiment of the present invention, the frame format of theframe protocol preferably includes the priority field, and if the datato be transmitted is real-time, the delay information is converted intothe priority information. The closer the data comes to the maximum delayor the more the delay is increased, the higher the priority is set.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a drawing showing a structure of the UMTS radio access network(UTRAN);

FIG. 2 is a drawing showing a protocol structure of the UMTS radiointerface;

FIG. 3 is a drawing showing a structure of radio access protocols forthe High Speed Downlink Packet Access (HSDPA) system;

FIG. 4 is a drawing showing a structure of the MAC layer supporting theHSDPA system;

FIG. 5 is a block diagram of the related art HSDPA scheduler in theMAC-hs sublayer;

FIG. 6 is a drawing showing a structure of a frame used in the HS-DSCHFrame Protocol; and

FIG. 7 is a block diagram showing a packet scheduler of the HSDPA systemin accordance with the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The HSDPA system should support both the real-time service andnon-real-time service. For non-real-time service, the scheduling methodcan be based on the related art service that is based on the relativepriority of data. However, for real-time service, the delay informationof data is preferably taken account in determining the transmissionpriority.

A packet transmission scheduling method in the HSDPA system of thepreferred embodiment provides a method for increasing the quality ofreal-time services.

In general, the data delay of the real-time service signifies thetransmission delay of the data between end users or between an end userand a server. The delay can occur at diverse parts of transmissionpaths, such as in the radio interface, UTRAN, core network, or the like.

Every delay that occurs in the various parts should be taken intoaccount, but it is not easy to consider the diversity of the delay inall of the regions in the network. Thus, the UMTS separates the delay inUTRAN from the delay in the other network elements. For example, thetransmission delay of real-time data should not exceed a maximum 250 msbetween the UE and the SGSN (or MSC).

As for the transmission path in the HSDPA system, the data coming intothe core network from an outside network is delivered to the RNC of theUTRAN through the SGSN or the MSC, and finally transferred to the NodeB. In the UTRAN, a transmission buffer is located at the RNC (RLC layer)and the Node B (MAC layer). In order to consider the delay of thereal-time data, the delay information at the RLC layer or the MAC layerneeds to be considered.

In particular, since the HSDPA scheduler in the Node B substantiallyhandles the data transmission, the scheduler needs to use the delayinformation for transmission. The delay information of the HSDPAscheduler can be divided into two types. One is the delay generated atthe RNC, and the other is the delay at the Node B.

First, let us consider the delay in the RLC layer. In order for thedelay information at the RNC to be used in the HSDPA scheduler, thecorresponding data and its related delay information need to betransmitted together to the Node B. That means the delay information istransmitted to the Node B through the lur interface or the lubinterface.

If the HSDPA system supports real-time services, the conventionalHS-DSCH FP can be adopted to transmit the data delay information.However, since there is no space for delay information in the frameformat of the frame protocol, some corrections should be made therefore.An example of the format will be described later.

On the other hand, a timer is required to measure the delay of data atthe RLC layer. However, a new timer is not necessary; rather, the timerused in the related art UMTS can be used. For example, the discard timercalled Timer_Discard is ready at the RLC layer to measure the lapse oftime until each RLC SDU is successfully transmitted after arriving atthe RLC layer. The value of the discard timer can be used as the delayinformation at the RLC layer.

Next, another delay information that the HSDPA scheduler can use isgenerated by the Node B itself. The delay can be measured by a timerafter the data is transmitted to the MAC layer in the Node B.

FIG. 7 is a block diagram showing an operation of the schedulerpositioned at the MAC-hs sublayer in accordance with the preferredembodiment of the present invention. Referring to FIG. 7, the MAC-hssublayer positioned at the Node B receives real-time data from the upperlayer and also receives scheduling control information related to thedata. The scheduling control information can include relative priorityinformation of the data, delay information of the data, the amount ofstored data in the upper layer, or the like.

A control information management unit 209 maintains the schedulingcontrol information received from the upper layer, and determineswhether the data has been transmitted based on the transmissioninformation coming from the storage unit (step S210). The controlinformation is shared by the scheduler and used as basic schedulinginformation.

The data in the MAC-hs sublayer is stored in the storage unit 201, andtransmitted according to the decision of the scheduler 207. The storageunit 201 transmits information regarding the buffer status to thescheduler 207 (step S212). The status information can include the datapriority, the amount of upper layer data, the amount of data in thestorage unit, and the delay information of data.

The timer that measures the elapsed time of data can be located at thestorage unit or at the control information management unit 209. In FIG.7, it is assumed that the timer is located at the storage unit 201. Theinitial value of the timer can be set to the elapsed time of the data inthe upper layer. Since the elapsed time in the upper layer can be storedin the control information management unit 209, it can be transferredusing the delay information (step S211). If necessary, the initial valueof the timer can be set to 0, which means that only the delay in thestorage unit 201 is used for the delay information of data.

Next, the scheduler 207 receives buffer status information from thestorage unit 201 (step S212) and receives channel status informationfrom the physical layer 205 (step S212). Based on the buffer statusinformation from the storage unit 201 and the channel status informationfrom the physical layer 205, the scheduler 207 performs the transmissionscheduling of data. The scheduler 207 determines the size of the datablock to be transmitted, and selects the MAC-hs SDUs to be contained inthe data block. PCI and TSN are also added to the organized data block.Transmission control information is then provided to the storage unit201 and the HARQ 203, and the data block is then transmitted to the HARQblock 203 and transmitted through the physical layer 205 (steps S214 andS215).

After transmission of the data block, the HARQ 203 provides atransmission result to the storage unit 201 (step S216). If the datablock has been successfully transmitted, the storage unit 201 discardsthe corresponding data (MAC-hs SDUs) from the unit, and also deletes thescheduling control information related to the data from the controlinformation management unit 209. The storage unit 201 then informs thescheduler 207 of the transmission result (step S217). If the data blockfails to be transmitted, the HARQ block 203 informs the scheduler 207 ofthe failure, so that the scheduler 207 can retransmit the data block(S217).

There are two methods for managing the delay information of data.

The first method is to use the total delay of data. In this method, thedelay of data comes from diverse parts of the network. That is, in orderto take into account the delay in the MAC-hs sublayer and the delay inthe upper layer (e.g. RLC layer), the delay at the MAC-hs sublayer andthe delay in the upper layer are summed. The summed delay of data can bethought of as the accurate delay, because all aspects of delay areconsidered.

The second method is adopted when the delay of data in the upper layercan be ignored, or when the delay of data at the MAC-hs sublayer is themajor portion of the delay. In such a case, because the delayinformation at the upper layer is not necessary, only the delay in theMAC-hs sublayer is considered.

In both the methods, when the MAC-hs SDU is received from the upperlayer, the storage unit of the MAC-hs sublayer starts to measure thedelay of the corresponding data. In the first method, the delay in theupper layer is delivered together with the related data, and added tothe delay in the MAC-hs sublayer. The total delay of the data isreported to the scheduler. In the second method, conversely, only thedelay in the MAC-hs sublayer itself is reported to the scheduler.

Referring to the first method, since the delay information in the upperlayer is transmitted through the lur or the lub interface, a new systemstandard is required between heterogeneous systems. Solutions for thiswill now be described.

The delay information in the upper layer is transmitted to the MAC-hssublayer by the HS-DSCH FP as shown in FIG. 6. However, since there isno field for transmitting the delay information using the HS-DSCH FP, anadditional field is required.

The value of the delay field can include the actual delay information.However, since the value of the field is to be expressed as a digitalvalue, it is necessary to express the field value in a suitable form.For example, if a delay time is 95.32 ms, the whole and accurate valuemay not be transmitted. In the field of the HS-DSCH FP, the delay of95.32 ms is converted to a suitable digital value based on the time unitsuch as 1 ms unit or 2 ms. For example, if the reference unit is 1 ms, avalue of 95 is set.

In the preferred embodiment, the delay is expressed with the unit ofTTI, a basic transmission time unit used in the HSDPA. The reason isbecause the scheduler transmits the data in the TTI unit.

In general, the maximum delay allowed by UMTS is about 250 ms. Theelapsed time in the upper layer should not exceed this value.Accordingly, if the TTI is 2 ms, the maximum value of the field is 125.Thus, with 7 bits, it would be sufficient to provide the delayinformation.

Consequently, because the new field of the frame format is required toexpress the delay of data, a new and different frame format structureneeds to be used. Two solutions are proposed hereinbelow.

The first method uses two independent frame formats for real-time andnon-real-time data, respectively. In general, delay information is notrequired for the non-real-time data, while priority information is notneeded for the real-time data. Thus, for non-real-time data, the sameframe format as the related art frame format can be used as it is.However, for real-time data, a field containing the delay information isnecessary and the priority information (CmCH-PI) field can be removed.In addition, in order to differentiate the two frame formats, anadditional indication field is required in the header of the frameformat. For example, using a ‘1’ can indicate the format fornon-real-time data, while a ‘0’ can indicate the format for real-timedata.

The second method uses one frame format for both real-time andnon-real-time data. For this purpose, the frame format of the currentHS-DSCH FP needs to be extended. The extended frame format preferablyincludes a field for delay information. In this method, some fields inthe frame format can be disabled depending on types of data. Forexample, for the non-real-time data, the delay field is not used, whilefor the real-time data, the priority field is not used. In order torecognize the field being used, a field indicating the type of datashould be additionally included in the header of the frame format.

In the above description, diverse methods for transmitting the delayinformation via the network interface have been discussed. However, someservice providers are not willing to change the current system.Consequently, the current frame format should support the real-time andnon-real time data. But, as described before, there is currently nofield for delay information.

One way to overcome this problem is to convert the delay informationinto the priority information. The priority means the urgency level ofdata. Thus, the higher the priority, the faster the data will betransmitted. This means that the scheduler can adjust the transmissiondelay with the priority. If the delay is properly converted to thepriority value, then the real-time service can be supported.

Thus, the upper layer monitors the delay of data to determine thetransmission urgency level. When the upper layer includes the data inthe frame format of HS-DSCH FP, it converts the delay into theappropriate priority value and includes it in the priority field of theframe format. For example, if the delay of the data reaches the maximumdelay limit, the corresponding data is given a high priority. Generallyspeaking, the real-time data would have a relatively high prioritybecause the non-real-time traffic is not time-sensitive.

Finally, the scheduler in the MAC-hs sublayer should be aware of themaximum transmission delay (T_MAX) for each real-time service. Assumethat the delay of the MAC-hs SDU (T_Total) means the total delay of thedata in the UTRAN. If the delay in the upper layer is considered T_Totalcorresponds to the sum of the delay in the upper layer T_RLC and thedelay in the MAC layer T_MAC (T_Total=T_RLC+T_MAC). If the delay is onlyin the MAC-hs sublayer, T_Total=T_MAC.

Accordingly, the scheduler transmits the emergent data first. Thatmeans, the smaller the difference between T_MAX and T_Total(T_MAX−T_Total) is, the faster the data is transmitted. If T_MAX−T_Totalis smaller than ‘0’, the corresponding MAC-hs SDUs are discarded becausethey have no meaning in the real-time service.

If the delay of the data in the upper layer is converted into thepriority, the scheduler transmits the data with the highest priorityfirst. If the value of T_MAX−T_Total becomes smaller than ‘0’, thecorresponding data is discarded in the MAC-hs sublayer.

The maximum transmission delay of data in the HSDPA scheduler isreceived from the RNC when the service is established. This informationcan be transmitted through the lur interface or the lub interface. Inparticular, the Radio Network Subsystem Application Part (RNSAP)protocol defined in the Iur interface of UMTS or Node B Application Part(NBAP) protocol defined in the lub interface of UMTS can be used.

The packet scheduling method for the HSDPA system in accordance with thepreferred embodiment has many advantages.

For example the HSDPA scheduler in the Node B can support both real-timeand non-real-time services with the delay of data and the priority levelof data, respectively.

Additionally, the results can be achieved by using the existing frameformat or by implementing a new frame format.

Moreover, real-time data can be prioritized over non-real-time data forefficient transmission.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method of transmitting data in a High Speed Downlink Packet Access(HSDPA) system, the method comprising: including data to a frame, theframe is related to a HS-DSCH (High Speed Downlink Shared Channel);including delay information to the frame, the delay informationindicating a data transmission delay or a latency of the data; includingan indicator to the frame, the indicator indicating whether the delayinformation is present; and transmitting, to a scheduler, the framecomprising the data, the delay information and the indicator.
 2. Themethod of claim 1, further comprising: including user buffer sizeinformation to the frame.
 3. The method of claim 1, wherein the delayinformation is a value based on the time unit of 1 ms or 1 TTI(Transmission Time Interval).
 4. The method of claim 1, wherein the datais real-time data.
 5. The method of claim 1, wherein the data is atleast one MAC-hs service data unit (SDU).
 6. The method of claim 1,wherein the scheduler obtains buffer status information and channelstatus information.
 7. The method of claim 1, wherein the scheduler islocated in a medium access control-high speed (MAC-hs) sub-layer, andthe MAC-hs sub-layer supports a hybrid automatic repeat request (HARQ)function.
 8. The method of claim 1, wherein the scheduler is located ina base station (Node B), and the base station (Node B) supports a hybridautomatic repeat request (HARQ) function.
 9. A method of transmittingdata in a High Speed Downlink Packet Access (HSDPA) system, the methodcomprising: receiving, by a scheduler, a frame comprising data, delayinformation indicating a data transmission delay or a latency of thedata, and an indicator indicating whether the delay information ispresent, wherein the frame is related to a HS-DSCH (High Speed DownlinkShared Channel); scheduling, by the scheduler, the data using the delayinformation in the received frame, wherein the delay information isidentified by the indicator; and transmitting the data according to thescheduling of the scheduler.
 10. The method of claim 9, wherein theframe further comprises user buffer size information.
 11. The method ofclaim 9, wherein the delay information is a value based on the time unitof 1 ms or 1 TTI (Transmission Time Interval).
 12. The method of claim9, wherein the data is real-time data.
 13. The method of claim 9,wherein the data is at least one MAC-hs service data unit (SDU).
 14. Themethod of claim 9, wherein the scheduler obtains buffer statusinformation and channel status information.
 15. The method of claim 9,wherein the scheduler is located in a medium access control-high speed(MAC-hs) sub-layer, and the MAC-hs sub-layer supports a hybrid automaticrepeat request (HARQ) function.
 16. The method of claim 9, wherein thescheduler is located in a base station (Node B), and the base station(Node B) supports a hybrid automatic repeat request (HARQ) function.